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All the ConnectionPoolDataSource and
DataSource implementations can be stored
in JNDI. In the case of the nonpooling
implementations, a new instance will be created every time the
object is retrieved from JNDI, with the
same settings as the instance that was stored. For the
pooling implementations, the same instance will be retrieved
as long as it is available (e.g., not a different
JVM retrieving the pool from
JNDI), or a new instance with the same
settings created otherwise.
In the application server environment, typically the
application server's DataSource instance
will be stored in JNDI, instead of the
PostgreSQL™
ConnectionPoolDataSource implementation.
In an application environment, the application may store
the DataSource in JNDI
so that it doesn't have to make a reference to the
DataSource available to all application
components that may need to use it. An example of this is
shown in Example 11.2, “DataSource JNDI Code Example”.
Example 11.2. DataSource JNDI Code Example
Application code to initialize a pooling DataSource and add
it to JNDI might look like this:
PGPoolingDataSource source = new PGPoolingDataSource();
source.setDataSourceName("A Data Source");
source.setServerName("localhost");
source.setDatabaseName("test");
source.setUser("testuser");
source.setPassword("testpassword");
source.setMaxConnections(10);
new InitialContext().rebind("DataSource", source);
Then code to use a connection from the pool might look
like this:
Connection conn = null;
try {
DataSource source = (DataSource)new InitialContext().lookup("DataSource");
conn = source.getConnection();
// use connection
} catch (SQLException e) {
// log error
} catch (NamingException e) {
// DataSource wasn't found in JNDI
} finally {
if (con != null) {
try { conn.close(); } catch (SQLException e) {}
}
}